(a) Field of the Invention
The present invention relates to a polyester fiber that can be applied to a fabric for airbag, and particularly to a high strength, high elongation, and high shrinkage polyester fiber having superior mechanical property, dimensional stability, packing property, and the like, a method of preparing the same, and a fabric for airbag using the same.
(b) Description of the Related Art
Generally, airbag is an apparatus for protecting a driver and passengers by providing a gas into the airbag by exploding gunpowder so as to inflate the airbag after detecting crash impact with an impact detecting sensor, when a driving car collides head-on at the speed of about 40 km/h or more, and a structure of a conventional airbag system is depicted in FIG. 1.
As depicted in FIG. 1, conventional airbag system includes an inflator 121 that generates a gas by ignition of a detonator 122; an airbag module 100 installed in a steering wheel 101 and including an airbag 124 that is expanded and unfolded toward a driver on driver's seat by the generated gas; an impact sensor 130 that gives an impact signal when the car is crashed; and an Electronic Control Module (ECM) 110 that ignites the detonator 122 of the inflator 121 according to the impact signal. In the airbag system, the impact sensor 130 detects the impact and gives the signal to the ECM, when the car collides head-on. At this time, the ECM 110 that received the signal ignites the detonator 122 and a gas generator in the inflator 121 is combusted. The combusted gas generator generates the gas rapidly and expands the airbag 124. The expanded airbag 124 contacts to the front upper body of the driver and absorbs the impact load caused by the collision partially, and when the driver's head and chest go forward according to the law of inertia and smash against the airbag 124, it further absorbs the shock toward the driver by rapidly discharging the gas from the airbag through discharging holes formed on the airbag. Therefore, the airbag absorbs the shock effectively that is delivered to the driver, and can reduce the secondary injury at the time of a head-on collision.
As disclosed above, the airbag for a car is prepared into a certain shape and installed in a steering wheel, side glass windows, or side pillars of the car in a folded form so as to minimize the volume, and it is expanded and unfolded when the inflator 121 operates.
Therefore, it is very important that the airbag has the folding property and the flexibility for reducing the shock to the passenger in addition to good mechanical property of the fabric for maintaining the folding and packaging properties of the airbag effectively when it is installed in a car, preventing the damage and rupture in the airbag itself, providing good unfolding property of the airbag cushion, and minimizing the impact provided to the passenger. However, the airbag fabric that can maintain superior air-tightness and flexibility for the passenger's safety, endure the impact applied to the airbag sufficiently, and be effectively installed in a car has not been suggested yet.
Previously, polyamide fiber such as nylon 66 has been used as the raw material of the fiber for airbag. However, nylon 66 has superior impact resistance but is inferior to polyester fiber in humid heat resistance, light resistance, and shape stability, and expensive.
Meanwhile, Japanese patent publication No. Hei 04-214437 suggested the polyester fiber for reducing such defects. Particularly, when the airbag was prepared by using prior polyester fiber, the fineness of the fiber was low in order to be installed in a narrow space in a car. However, the polyester fiber having low fineness leads to the drops of strength and toughness, and there was a limitation for maintaining sufficient mechanical property, air-tightness, and unfolding property at the severe conditions of high temperature and high humidity.
Therefore, it is needed to develop the fiber that maintains superior shape stability and air-tight effect so as to be used for an airbag fabric, and also maintains flexibility for reducing the impact applied to passengers, the packing property, and superior mechanical properties at the severe conditions of high temperature and high humidity.